Method

• 1.
  Soak the porcini in 2/3 cup (160ml) boiling water for 15 minutes or until softened.
• 2.
  Heat half the butter in a large frypan over medium heat. Add leeks and thyme. Cook, stirring occasionally, for 5 minutes or until leeks have softened. Add ¼ cup (60ml) water, cover loosely and cook for 8 minutes or until leeks are tender but not coloured. Uncover and cook 5 minutes or until liquid is gone. Transfer to a bowl and set aside.

• 3.
  Place frypan over high heat and melt remaining butter. Add Swiss brown mushrooms and cook, stirring occasionally, for 4-5 minutes until browned. Add garlic, porcini and porcini liquid. Cook 2-3 minutes or until liquid is gone. Set aside to cool.
• 4.
  Preheat oven to 200°C. Cut a 25cm round from 1 pastry sheet. Place on a paper-lined baking tray. Keep remaining sheet chilled.
• 5.
  Stir creme fraiche through cooled leek mixture. Spread half over the pastry round, leaving a 2cm border. Top with gruyere, then remaining leek mixture. Finish with cooled mushroom mix. Brush pastry border with beaten egg and top with remaining pastry sheet, pressing edges together to seal. Trim excess pastry to form a 25cm round and, using the back of a knife, score lines from the centre of the pastry to the outside edge. Brush top with beaten egg.
• 6.
  Bake for 25 minutes or until pastry top is golden. Reduce temperature to 170°C and bake 30 minutes or until bottom is golden.
• 7.
  Place mustard and vinegar in a bowl and slowly add the oil, whisking until combined. Toss witlof and radicchio in dressing and serve with slices of the warm pithivier.